1. Field of the Invention
This invention relates to method and apparatus for use in performing endoscopic surgical procedures. More particularly, this invention relates to a method and apparatus for performing a carpal tunnel release endoscopically.
2. Description of the Prior Art
Because of the trauma associated with open surgical procedures, efforts have been recently accelerated to develop endoscopic alternatives to all types of open surgical procedures. This invention relates to an endoscopic alternative to one such open procedure--the treatment of carpal tunnel syndrome, caused by the compression of the median nerve by the transverse carpal ligament. The treatment generally involves a procedure during which the carpal ligament is severed. While endoscopic versions of this procedure have been used in the past with varying degrees of success, continued development of endoscopic procedures to improve efficiencies and reduce patient trauma is always desirable.
Although the preferred embodiment of this invention relates to carpal ligament release, it will be understood by those skilled in the art that the method and apparatus disclosed herein may be easily adapted to other surgical procedures.
One system recently developed for the endoscopic treatment of carpal tunnel syndrome is described in U.S. Pat. No. 5,029,573 (Chow). Chow describes other prior art endoscopic carpal tunnel release procedures and claims his invention to be an improvement over the prior art in that the carpal ligament may be severed under direct viewing through an endoscope. As used herein, the term "endoscope" is intended to be generic and refers to any type of optical system used to view the interior of a patient. In the Chow procedure a cylindrical sheath, open at both ends and having a longitudinal slot in its periphery, is inserted through an incision in the wrist, under the carpal tunnel and out through an incision in the patient's palm. An endoscope is inserted in one end of the cannula and a cutting instrument is inserted in the other so that its cutting blade protrudes out of the longitudinal slot in order to cut the carpal ligament.
While the Chow procedure is undoubtedly an improvement over open surgical procedures, the necessity to use two portals, one of them being in the palm, is a disadvantage which it would be preferable to avoid. One prior art system--the Agee Inside Job.TM. Carpal Tunnel Release System--has been known to provide a single portal endoscopic carpal tunnel release procedure. While avoiding some disadvantage associated with Chow's procedure and instruments, the Agee system has other disadvantages. The Agee system utilizes a cannula having a small proximal window through which a knife may be projected under the control of a trigger on a handpiece. The knife has a retrograde cutting edge and retraction of the knife cuts the carpal ligament. This type of motion has been found difficult to adequately control. Accordingly, while it is an object of this invention to produce a method and apparatus for the endoscopic treatment of carpal tunnel syndrome which avoids the necessity to create two incisions, it is also an object to produce a single portal method and apparatus which is easier to use than known single portal procedures and instruments.
An additional disadvantage associated with the Chow procedure is the relatively large number of cutting instruments required during the course of the procedure. This not only adds to the cost of the instrumentation but also adds to the time required to complete the procedure, thereby creating additional trauma for the patient. The Agee system, while having only one disposable blade assembly, has a complex, non-disposable handpiece. It is consequently another object of this invention to produce a method and apparatus for the endoscopic release of a carpal tunnel ligament using a minimum of instruments in order to simplify the procedure and minimize the amount of time required for its completion.
Another difficulty with prior art endoscopic carpal ligament release systems is that the cannula inserted under the carpal ligament is cylindrical, thereby making it hard to align the longitudinal slot or window properly and hold it in place during the cutting step. Prior art slotted cannulas have been found to rotate easily during the surgical procedure. It is extremely important that the cannula be maintained with the slot facing the ligament, even during manipulation of the scope, so that the surgeon can be assured that the slot does not face any critical features such as the median nerve. Therefore, it is another object of this invention to produce a method and apparatus which facilitates the alignment of a cannula under the carpal ligament.
It is still another object of this invention to produce an endoscopic surgical procedure and apparatus suitable for use in surgical procedures other than carpal ligament release.
It is yet another object of this invention to produce disposable instruments for use in endoscopic carpal ligament release procedures as well as other endoscopic surgical procedures.